A test setup of this kind is already known, where the scanning of the bottle bottom for foreign matter particles is done entirely by the mirror element radially outward from the axis of the front face of the rotor, which, upon a complete revolution of the rotor, scans the entire bottom of the bottle. This known method of inspection generally yields good results. Small particles, however, located exactly in the central area of the bottom of the bottle are not always detected. They are only partially discerned by the concave mirror element and the change in light quantity or intensity impinging upon the photocell during one revolution of the mirror segment is correspondingly small.